According to an S8HR roaming architecture for internet protocol multimedia subsystem (IMS) call support, an ordinary IMS call of user equipment (UE) that is roaming within a visited public land mobile network (VPLMN) may be routed through a packet data network gateway (PGW) and proxy call session control function (P-CSCF) node that are both located within a home public land mobile network (HPLMN) of the UE. However, an IMS emergency call of the UE may need to be routed through a PGW and P-CSCF node that are both located within the VPLMN, so that the IMS emergency call will be placed with a public safety answering point (PSAP) that is located within relatively close proximity to the UE. If no session initiation protocol (SIP)-based network-to-network interface (NNI) exists between the VPLMN and the HPLMN, the P-CSCF node that handles the IMS emergency call in the VPLMN may be unable to directly communicate with a home subscriber services (HSS) node in the HPLMN.